I don’t think you’re being irrational or over-reacting.

In your place, I may still be okay with being charged (the money as such wouldn’t bother me) but after seeing a T for two years with the sort of perfect record that you’ve mentioned having, it would really bother me if she did it without talking to me first....in a lot of depth.

I broke up with my hair stylist for similar reasons — I expect far more from my therapist!

ETA: Sorry, I missed the part where you said you cancelled because you were sick (thought it was just a random cancellation). Then it’s really not okay that she did that.